Telephone-exchange system



A. H. DYSON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED IAN- 30,1917. 1,334,294, Patented Mar. 23, 1920.

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TELEPHONE EXCHANGE SYSTEM.

APPLICAIION FILED JAN- 30,1917. '1 3%4 ,Q;94, Patented Mar. 23, 1920.

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A. H. DYSON.

TELEPHONE EXCHANGE SYSTEM.

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A. H, DYSON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JAN-30,1917.

Patented Mar. 23, 1920.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JAN-30,1917.

1 34,294. Patented Mar. 23, 1920.

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UNITED STA' 1 ES PATENT, ornion.

ALFRED H. DYSON, OF MONTCLAIR, NEW JERSEY, ASSIG-NOR T WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Specification of Letters Patent.

TELEPHONE-EXCHANGE SYSTEM.

Patented Mar. 23, 1920.

Application filed. .Tanuery 30, 1917. Serial No. 145,367.

a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and particularly to circuit arrangements for automatic or semi-automatic telephone exchanges.

It is the object of the resent invention to provide an automatic telephone exchange system in which the seizure of a selected line by a switching device is controlled by means provided in common to a plurality of such switching devices.

With this object in view, according to the main feature of the present invention, a selectively, operable switching device, such as a final selector or connector switch, is set on to the terminals of aline, such as the called line, without any regard to the busy or idle condition of the line, the testing means for determining whether the called line should or should not be seized being provided in association with another selector switch employed in extending a line toward said connector switch.

According to another feature of the present invention means are provided for permitting the successful operation of the aforementioned testing means without regard to the busy, or idle, condition of the called line whereby the seizure of a busy called line is made possible.

Other features of the invention will readily appear from the subsequent detailed description and the appended claims.

In the drawings Figures 1 to 6 show a semi-mechanical exchange diagrammatically, only so much being shown as is neces sary for a clear understanding of the present invention. Fig. 2 should be placed to the right of Fig. 1; Figs. 3, 1 and 6 in sequence below Fig. 1, and Fig. 5 to the rightof Fig. 4.

The selector, connector and cord finder switches may be of the type described in a Patent 1,123,696 to E. B. Craft and J. N.

Reynolds, granted January 5, 1915, the cord finder switch having only one set of wipers. The sequence switches may be of the type described in a Patent 1,127,808 to J. N.

Reynolds and C. F. Baldwin, granted February 9, 1915. The sequence switches, shown in Figs. 1 and 2, control the contacts diagrammatically indicated in the respective figures, and. the sequence switch, shown in Fig. 3, controls the sequence switch contacts shown in Figs. 3, A and 6. An allotter shown within the dotted lines in Fig. 3, may be of the same type as the sequence switches.

It will be obvious to those skilled in the art that, instead of the types of selector switches and controlling apparatus disclosed in the present application, switches and controlling apparatus of a widely varying character may be employed without departing from the spirit of the invention.

An A operator desiring to extend the line of a calling subscriber to a called substation 200, communicates through a wellknown order wire (not shown) with a B operator located at the exchange in which the line of the called subscriber terminates and transmits to her the number of the called line, which in the present case will be assumed to be No. 9851. The B operator instructs the A operator to extend the calling line through her cord circuit to an idle trunk leading to the B operators position. Assuming that this idle trunk is the one shown in Fig. 1, the A operator inserts her plug 100 into a jack 101 provided at her position. A relay 102 is included thereupon in a circuit extending through plug 100 and jack 101, which circuit is completed through a secondary winding of the Well-known repeating coil in the cord circuit of the A operator. Relay 102 closes then a circuit from ground through its front contact and armature, and the winding of a relay 103 to grounded battery. Relay 103 becomes energized.

The B operator depresses then her assignment key 17 9 for the purpose of causing the cord finder 300 to connect an idle registersender to the trunk seized by the A operator. In response to the closure of key contact 104:, a circuit is closed from the plus pole of battery through the contact of this key, the upper left-hand contact of a sequence switch spring 105, and the power magnet of sequence switch 106 to the minus pole of battery. The sequence switch 106 is moved -out of position 1 and under the control of .its master contact 107 into position 2. In

response to the closure of assignment key contact 180,.another sequence switch corresponding to 106, the associated assignment key of Which is not actuated and which is standing in position 2, will be driven out of'that position,'thedrivingcircuit being closed through a sequence switch contact corresponding to 181. In this manner the Simultaneous assignment of two trunks belonging to the same group. is prevented. When the sequence switch 106 reaches position 2, a. circuit is closed from the plus pole of battery through the left-hand armature and back contact of a relay 108, the lower contacts of a sequence switch spring 109, conductor 301, the left-hand contacts of a sequence switch spring 302, and'the winding of a relay 303 to the minus pole of battery. The relay 303 becomes energized and closes a circuit from the plus pole of battery,

through its right-hand armature and front,

contact, the right-hand contact of sequence switch spring 304, and the power magnet of sequence switch 305 to the minus pole of battery. The sequence switch 305 is moved out of position 1 and under the control of its master contact 306, into position 2. When the sequence switch 305 moves through position 1%, the circuit of relay 303 is interrupted at the upper left-hand contact of sequence switch spring 302, this relay, however, remains energized by current flowing through a circuit extending from the minus pole of battery, through its winding, the lower left-hand and upper right-hand contacts of sequence switch spring 302, and the left-hand back contact and armature of a relay 307, to the plus pole of battery. When the sequence switch 305 reaches position 2, a circuit is closed from the minus pole of battery, through the winding of a magnet 308, the upper contacts of a seuence switch spring 309, the right-hand i ront contact and armature of the-relay 303, to the plus pole of battery. -Magnet 308, by attractingits armature, presses a brush rod 310 of the cord finder against a roller 311 constantly rotating in the direction indicated by the arrow. Under the control of this roller the wipers and the commutator brush of the cord finder are caused to move in an upward direction. As soon as a test wiper 312 engages a. test terminal 313 individual to the trunk assigned by the B operator, a circuit is closed from the minus pole of battery, through the winding of relay 307, the right-hand contact of sequence switch spring 314, wiper 312, terminal 313, conductor 315, sequence switch contact 110, and the right-hand back contact and armature of a relay 111 tothe plus pole of battery. Relay 307 becomes energized and closes a locking circuit for itself from the plus poleof battery, through its left-hand armature and front contact, the upper lefthand contact of sequence switch spring 314 and the winding of relay 307, to the minus pole of battery, and another lockin circuit extending from the minus pole 0' battery through its Windin the lower contact of sequence switch sprlng 314, the right-hand front contact and armature of this relay, the winding of relay 316, cord finder wiper 317, terminal 318, conductor 319, the lower right-hand and upper left-hand contacts of a sequence switch spring 112, the winding of relay 108, the right-hand contacts of a sequence switch spring 113, the left-hand back contact and armature of relay 111, and sequence switch contact 114 to the plus pole of battery. Relays 316 and 108 become energized. Relay 108 opens the originally traced circuit of relay 303, the locking circuit of this latter mentioned relay being open in the left-hand back contact of relay 307. As long, however, as the wipers of the cord finder are not exactly centered on the selected set of terminals, which fact is indicated by this, that the commutator brush 320 engages a conductingplate 321, the relay 303 does not become deenergized, a circuit being closed from the minus pole of battery, through its Winding, left-hand front contact and armature, conducting plate 321 and brush 320 to the plus pole of battery. As soon as the cord finder wipers are centered on the selected set of terminals, the brush 320 is in engagement with one of the insulated segments 322 in the conducting plate 321, and the above traced lockin circuit of relay 303 is opened. Relay 303%)6COII16S de'e'nergized and closes a circuit from the plus pole of battery through its right-hand armature and back contact, the lower left-hand contact of sequence switch spring 304 and the power magnet of sequence switch 305 to the minus pole of battery, for moving this sequence switch out of position 2 and into position 3.

In the meantime, the B operator has de pressed keys numbered 9, 8, 5 and 1 in the thousands, hundreds, tens and units rows of keys, respectively (see Fig. 5'). In response to the depression of the No. 9 thousands key. a circuit is closed from the plus pole of battery through contact 500, the No. 9 thousands key, a conductor 501, the left-hand winding of a relay 401, the upper right-hand contact of a sequence switch spring 402, the lower contact of sequence switch spring 403. conductor 404, the left-hand contact of an allotter spring 325, the winding of a relay 326, the left-hand contact of an allotter spring 327 and the upper right-hand contact of a sequence switch spring 328 to the minus pole of battery. Relays 401 and 326 become energized. The relay 326 closes a lockin circuit for itself and the relay 401 from t e minus pole of battery through the right-hand armature and front contact of 'left-hand winding of a relay 405, the lower right-hand contact of a sequence switch spring 406 and thence through the path traced for relay 401 to the minus pole of battery. Relay 405 becomes energized.

The depression of the No. 8 hundreds key results in the closure of the following circuits: from the plus pole of battery through contact 504, conductor 505, the left-hand winding of a relay 407, the upper righthandcontact of a sequence switch spring 408, and thence through the path traced for relay 405 to the minus pole of battery; and from the plus pole of battery through contact 506, conductor507, the right-hand winding of a relay 409, the lower left-hand contact of sequence switch spring 406, and thence through the same path as traced for the above mentioned relays, to the minus pole of battery. Relays 407 and 409 became energized. The relay 409 closes a cirvcuit from grounded battery through its an mature and front contact and the winding of a relay 410 to ground, whereupon this relay also becomes energized.

The depression of the No. 5 tens key results in the closure of the following circuit: from the plus pole of battery through contact 508, conductor 509, the left-hand winding of a relay 411, the upper lefthand contact of a sequence switch spring 412, and thence through the lower contact of sequence switch spring 403 to the minus pole of battery. Relay 411 becomes energized.

The depression of the No. 1 units key re sults in the closure of a circuit from the plus pole of battery through contact 510, conductor 512, the left-hand winding of a relay 413, the lower right-hand contact of a sequence switch spring 414, and thence through the lower contact of sequence switch spring 403 to the minus pole of battery. The relay 413 becomes energized.

A circuit is then closed from the plus pole of battery through the left-hand contact of sequence switch spring 323, the winding of relay 324, conductor 400, the right-hand armature, front contact and right-hand winding of relay 413, the right-hand armature, front contact and winding of relay 411 to the minus pole of battery. The relay 324 becomes energized and closes a circuit from the plus pole of battery, through its front contact and armature, the winding of a relay 330, conductor 420, the right-hand armature, front contact and winding of relay 407, the ri ht-hand winding of relay 405, the right-hen armature, front contact and winding of relay 401, and the left-hand winding of relay 409 to the minus pole of battery. Relay 330 becomes energized and closes a circuit from the plus pole of battery, through the right-hand contact of sequence switch spring 323, its front contact and armature, and the power ma net of sequence switch 305 to the minus poi of battery, for moving this sequence switch out of position 3 and into position 4.

When the sequence switch 305 reaches position 4, two circuits are closed from the minus pole of battery, through the lower contacts of sequence switch spring 328, eonductors 531, 422, and the windings of magnets 520, 521, 52 2 and 523, to the plus pole of battery. These magnets upon energlzation cause the release of the depressed keys, the relays that were originally energized through contacts of these keys being held up I through the above traced locking circuits, with the exception of relay 326, which becomes deenergized. Upon the deenergization of relay 326, a circuit is closed from the plus pole of battery, through the upper contact of allotter spring 348, the left-hand back contact and armature of relay 326, the upper contact of sequence switch spring 340, and the power magnet of sequence switch 305, to the minus pole of battery. The sequence switch is moved out of position 4 into position 5. A circuit is now completed from the plus pole of battery, through the lefthand contact of allotter spring 348, the lower contacts of sequence switch spring 309, to the power magnet of allotter 345, to the minus pole of battery. The allotter is moved out of position 1 and under the control of its master contact 360 into position 2. In this position of the allotter the sequence switch associated with another cordfinder is moved into position 1, in a manner to be hereinafter described.

In positions 5 and 2 of sequence switches 305 and 10-6, respectively, a fundamental circuit is closed from the plus pole of battery, through the armature and back contact of the counting relay 0, conductor 601, the windings of a stepping relay 332, a resistance 334, the left-hand contact of a sequence switch spring 335, the front contact and armature of relay 316, cord finder wiper 336, terminal 337, conductor 338, the

locking circuit for itself through its lefthand front contact and armature and the spring 116.

Relay 332 closes a circuit from -the plus pole of battery through its front contact and armature, the upper contacts of sequence switch springs 339 and 331, conductor 423,:"thelefty-l1and armature and front contact of relay 40,1, conductor 600, the armature and back contact of counting relay 4', and the winding of counting relay 4 to the minus pole of battery. Counting relay 4 becomes energized and closes a looking circuit for itself extending from the minus pole of battery, through its winding, the winding of counting relay 4, the front contact and armature of counting relay 4, and the sequence switch contact 602 to the plus pole of battery. Relay 4, due to a shunt path closed around its winding through the front contacts of register relay 401 and relay 332, cannot become energized.

Upon energization, relay 117 closes a circuit from plus pole of battery through its right-hand armature and front contact, the lower right-hand contact of a sequence switch spring 118, and the power magnet of sequence switch 106 to the minus pole of battery, for driving this sequence switch out of position 2 and into-position 3. In positions 3 to 12 of sequence switch 106, a circuit is closed from ground, through an interrupter 182, the upper left-hand and lower right-hand contacts of sequence switch spring 183, and a lamp 184, to grounded battery. The flashing of lamp 184 indicates to the. B operator that the sender has rotating in the direction indicated by the arrow. Under the control of roller 123, the wipers and brushes carried by rod 121 are moved in an upward direction. As soon as a brush 124 engages a conducting plate 125, a shunt path is closed from the plus pole of battery, through the upper contact of a sequence switch spring 126, brush 124, conducting plate 125, conductor 127, the upper left-hand contact of sequence switch spring 115, the lower left-hand contact of sequence switch spring 116, to the winding of the ture and back contact of counting relay 3,

the winding of counting relay 3 to the minus pole of battery.

cuit of the counting relay 3 is now completed and this relay operates in the same manner as relay 4. The relay 3 is permitted to energize as soon as relay 332 is deenergized, due to the engagement of the second insulated segment 128 by brush 124, and this operation continues until the brush 124 engages the fifth insulated segment 128, whereupon the counting'relay 0 becomes energized and opens in its back contact the fundamental circuit, whereupon the relays 332 and 117 become deenergized. The relay 117 opens the circuit of magnet 119, whereupon the selector 122 is arrested in its upward travel with the fifth set of its wipers below the first set of terminals in the fifth section of its terminal bank. Relay 0' closes a circuit from the plus pole of battery, through its armature and front contact, conductor 603, the lower left-hand contact of sequence switch spring 340, and the power magnet of sequence switch 305 to the minus pole of battery, for moving this sequence switch out of position 5 and into position 7. IVhile the sequence switch is moving from position 5 to 7, the locking circuit of the counting relays is opened and these relays release their armatures.

In response to the deenergization of relay 1.17, a circuit is closed from the plus pole of battery, through the right-hand armature and back contact of this relay, the lower left-hand contact of sequence switch spring 118, and the power magnet of sequence switch 106 to the minus pole of battery, for moving this sequence switch out of position 3 and into position 4.

When the sequence switch moves out of position 3 and opens the upper left-hand contact of sequence switch spring 112, the relay 108 becomes deener ized, the relays 307 and 316 that were lofired up in series with relay 108, are now supplied with plus battery through sequence switch contact 114. the left-hand back contact and armature of relay 111, and the right-hand contacts of sequence switch spring 112. When the sequence switch reaches position 4, a circuit is closed from the plus pole of battery, through the lower right-hand contact of sequence switch spring 129, and the winding of a trip ma net 130 to the minus pole of battery. rip magnet 130 becomes energized and moves a tripping finger 131 opposite a catch (not shown) provided on a cam, by means of which the wipers are held apart and out of the path of the contacts of the terminal bank.

' pole of battery, for moving this sequence switch out of position 4 and into position 5. The relay 117 remains locked up by a circuit completed through its left-hand front contact and armature and the lower lefthand contact of sequence switch spring 116? The relay 332, which became energized in series with relay 117, closes a circuit from the plus pole of battery through its front contact and armature, the upper contact of sequence switchspring 339, the lower lefthand contact of sequenece switch spring 331, conductor 425, the left-hand armature and front contact of relay 405, the left-hand armature and front contact of relay 410,

conductor 604, the armature and back contact of counting relay 3, and the winding of counting relay 3 to the minus pole of battery. Counting relay 3 becomes energized and closes a locking circuit for itself including the winding of the counting relay 3; the latter, however, cannot become energized as long as the stepping relay 332 is energized.

hen the sequence switch 106 reaches position 5, the above traced circuit of magnet 119 is again completed and this magnet causes the further travel of the brush rod tor 134, the upper right-hand contact of se quence switch spring 115, and the lower lefthand contact of sequence switch spring 116, to the winding of relay 117. The stepping relay 332 becomes denergized and permits the energization of the upper counting relay 3'. This shunt path is opened as soon as the brush 132 engages the first one of the insulated segments 135 provided in the conducting plate 133. During the successive engagement'of the conducting plate 133 and the insulated segments 135, the stepping relay 332 is operated to cause the actuation of the counting relays in the above described manner until the counting relay 0 is energized. The fundamental circuit is then openedtrelays 332 and 117 become de'e'nergized. In order to. insure the proper centering of the selector Wipers, as long as the wiper 132 is in engagement with the con ducting plate 133, the relay 117 is maintained energized by current flowing through the above traced path, the closure of which resulted in the shunting out of relay 332. The relay 0 closes the above traced circuit through conductor 603 and causes the sequence switch 305 to move out of position 7 and into position 9.

Upon the de'energization of relay 117, the magnet 119' becomes deenergizcd and acircuit is closed from the plus pole of batter through the right-hand armature and bac;

contact of this relay, the upper left-hand contact of a sequence switch spring 136, and the right-hand winding of a test relay 137 to grounded battery. Relay 137 becomes energized and closes a circuit from the minus pole of battery, through the power magnet of sequence switch 106, the upper contacts of a sequence switch spring 138, the left-hand front contact and armature of relay 137, and the right-hand back contact and armature of relay 111, to the plus pole of battery. The

sequence switch is thus moved out of position 5 and into position 6. The magnet 130 becomes. de'energized.

A circuit is now closed from the minus pole of battery through the winding of mag net 119, the lower contact of sequence switch spring 120, the left-hand front contact and armature of relay 137, and the right-hand back contact and armature of relay 111 to the plus pole of battery. Magnet 119 becomes energized and causes the further travel of the selector 112 for the purpose of selecting an idle trunk in the desired group. When the sequence switch 106 moves out of position 5 and opens the upper left-hand contact of spring 136, relay 137 does not become denergized, a circuit being closed from the minus pole of battery, through the left-hand winding of this relay, a sequence switch contact 139,-the right-hand front contact and armature of relay 137, the upper right-hand contact of sequence switch spring 140, a resistance 141,'test wiper 142 and the test terminal of the first trunk in the selected group, to the plus pole of battery, if such trunk is busy. As soon, however, as the test wiper 142 engages a test terminal 143 to which no ground is connected, and as soon as the path traceable from the minus pole of battery, right-hand winding of relay 137, the lower contact of sequence switch spring 136, conductor 144, conducting segment 145, brush 146, the right-hand contacts of sequence switch spring 138, the left hand front contact and armature of relay 137, righthand armature and back contact of relay 111, to the plus pole of battery, is opened, the relay 137 becomes deenergized. The circuit of the magnet 119 is now open and the selector is arrested in its upward travel with its wipers in engagement with the terminals of an idle trunk. A guarding circuit is now closed from the plus pole of battery, through the lower left-hand contact of sequence switch spring 129, the right-hand back contact and armature of relay 137, the upper right-hand contact of sequence switch spring 110, resistance 1+1, and wiper 112, to test terminal 113 and multiple thereof, whereby the seizure of this trunk by another selector is prevented. Upon the deenergization of relay 137, a circuit is closed from the minus pole of battery, through the power magnet of sequence switch 106, the upper right-hand contact of sequence switch spring 105, the left-hand back contact and armature of relay 137, and the right hand back contactand armature of relay 111 to the plus pole of battery, for moving the sequence switch 100 out of position 0 and into position 7.

Sequence switch 305 being in position 9, the above traced fundamental circuit is reestablished and relays 332 and 117 become energized. Relay 117 closes a circuit from the plus pole of battery through its righthand armature and front contact, the lower right-hand contact of sequence switch 118, and the power magnet of sequence switch 106 to the minus pole of battery, for moving this sequence switch out of position 7 and into position 8. The guarding potential is now connected through the upper contact of sequence switch spring 129 to the test terminal 113 and multiples thereof. A circuit is closed from the plus pole of battery, through the right-hand armature and front contact of relay 117, the upper left-hand contact of a sequence switch spring 117, selector wiper 118, terminal 119, trunk conductor 200, the lower left-hand contact of sequence switch spring 201, and the winding of a relay 202 to the minus pole of battery. Relay 202 closes a circuit from the plus pole of battery, through its left-hand armature and front contact, the upper right-hand and lower left-hand contacts of a sequence switch spring 203, and the winding of a relay 2041 to the minus pole of battery. Relay 204 becomes energized and locks up through a circuit traceable from the minus pole of battery through its' right-hand front contact and armature, a resistance 205, a conductor 206, test terminal 143, wiper 142, resistance 14:1 and the upper contact of sequence switch spring 129 to the plus pole of battery. Relay 204 closes a circuit from the plus pole of battery, through its left-hand armature and front contact, the upper right-hand contact of a sequence switch spring 207, and-the power magnet of sequence switch 208 to the minus pole of battery. This sequence switch is moved out of position 1 and under the control of its master contact 209, into position 2. When the sequence switch leaves position 1, the relay 202 is maintained energized,

through a locking circuit from the minus pole of battery, through the winding of this relay, the upper contact of sequence switch spring 210, the right-hand front contact and armature of relay 202, and the. lower righthand contact of sequence switch spring 201, to the plus pole of battery at the right-hand armature of relay 117.

\Vhen the sequence switch 208 reaches position 2, a circuit is closed from the minus pole of battery, through the winding of a magnet 211., the left-hand contact of sequence switch spring 210, the righthand front contact and armature of relay 202, the lower right-hand contact of sequence switch spring 201 to the plus pole of battery at the armature of relay 117. Magnet 211 attracts its armature. and presses a brush rod 212 of connector 213 against a highspeed roller 21-1, constantly rotating in the direction indicated by the arrow. The wipers and brushes carried by the rod are thus moved in an upward direction.

In response to the energization of relay 332, a circuit is closed from the plus pole of battery through the contact and armature. of this relay, the upper contact of sequence switch spring 335). the lower right-hand contact of sequence switch spring 331, conductor 42, the left-hand armature and front contact of relay 107, conductor 004-, the armature and back contact of counting relay 3', the winding of counting relay 3 to the minus pole of battery. The counting relay 3 becomes energized and closes a locking circuit for itself in the above described manner.

As soon as a commutator brush 215 of the connector engages a conducting plate 216, a shunt path is closed from the plus pole of battery, brush 215, conducting plate 216, conductor 217, the upper left-hand contact of sequence switch spring 218, trunk conductor 219, terminal 150, selector wiper 151, the upper right-hand and lower lefthand contacts of sequence switch spring 110, and the left-hand armature and front contact of relay 117. to the winding of this relay. Due to the closure of this shunt path, the relay 332 becomes deenergized and permits the energiz ation of the counting relay 3. As soon as the commutator brush 215 engages the first one of five insulating segments 220, the above traced shunt path is opened and the relay 332 is permitted to reenergize, whereupon the counting relay 2 becomes energized. The connector continues to travel until, upon the engagement of'the fourth insulated segment 220 by the brush 215, the relay 332 permits the energization of counting relay 0. The fundamental circuit is then opened, and relay 332, and, if the brush 215 is in engagement-with an insulated segment 220, the relay 117 also, becomes deenergized, and the latter opens the circuit of relay 202 and of magnet 211. Relay 0 closes the above traced circuit and causes sequence switch 305 to move out of position 9 and into position 11, whereupon the locking circuit of the counting relays is opened. Relay 117 closes a circuit from the plus pole of battery through its right-hand armature and back contact, and the lower left-hand contact of sequence switch spring 118, for causing se-' quence switch 106 to move out of position 8 and into position 9.

Upon the deenergization of relay 202 a circuit is closed from the plus pole of battery, through the left-hand armature and back contact of relay 202, upper left-hand and lower right-hand contacts of sequence switch spring 203, and the power magnet of sequence switch 208 to the minus pole of battery, for driving this sequence switch out of position 2.and into position 3.

Then sequence switches 106 and 305 reach positions 9 and 11, respectively, the fundamental circuit is again closed and relays 332 and 117 become energized. The relay 117 closes a circuit through the lower right-hand contact of sequence switch spring 118, for driving the sequence switch 106 out of position 9 and into position 10, and the above traced circuit for causing the energization of relay 202. This relay closes a circuit through the right-hand contacts of sequence switch spring 203, for driving sequence switch 208 out of position 3 and into position 4:, whereupon the actuating circuit of magnet 211 is again established through the lower left-hand contact of sequence switch spring 210. When the sequence switch 208 reached position 3 and closed the upper contact of sequence switch spring 221, a trip magnet 222 was energized and moved a trip finger 223 into a position such that, upon the initiation of the movement of the brush rod 212, the selected set of brushes may be tripped. The.

energization of relay 332 results in the closure of a circuit from the plus pole of battery, through the front contact and armature of this relay, the upper left-hand and lower right-hand contacts of sequence switch spring 339, conductor 126 the lefthand armature and front contact of relay 411, conductor 610, the armature and back contact of counting relay 5", and the winding of counting relay 5 to the minus pole of battery. Counting relay 5 becomes energized and prepares the energizing circuit of relay 5'. As soon as the commutator brush 221 connects plus battery through the conducting plate 225, conductor 226, and the upper right-hand contact of sequence switch spring 218, to the winding of relay 117, the stopping relay 332- is shunted out and permits the energization of the counting relay 5. When the commutator brush 224 engages the first oneof a plurality of in= sulated segments 227 provided in the conducting plate 225, the shunt path is removed from the winding of relay 117 and relay 332 is permitted to reenergize, whereupon the counting relay 4 becomes energized. The operation of the counting relays un-' der the control of the stepping relay 332 continues until, in response to the sixth engagement of the conducting segment 225 by brush 221, the counting relay 0 becomes energized and opens the fundamental circuit, whereupon relays 332 and 117 become deenergized, and the latter opens the circuits of relay 202, and magnet 211. The upward travel of the connector is arrested. Relay 0 closes the above traced circuit for driving the sequence switch 305 out of position 11 and into position 13, and relay 117 closes the circuit through its right-hand back'contact and the lower left-hand contact of sequence switch spring 118, for driving the sequencefswitch 106 out of position 10 and into position 11. The relay 202 closes the above traced circuit through sequence switch spring 203 for driving sequence switch 208 out of position a and into position 5. The magnet 222 becomes deenergized.

When the sequence switches 106 and 305 reach positions 11 and 13, respectively, the fundamental circuit is again closedwhereupon relays 332 and 117 become energized. Relay 117- closes the circuit through the lower right-hand contact of sequence switch spring 118 for driving the sequence switch 106 out of position 11 and into position 12, and a circuit for causing the energization of relay 202, which relay by closing its lefthand front contact causes the movement of sequence switch 208 out of position 5 and into position 6. In position 6 of sequence. switch 208, a circuit is closed from the minus pole of battery, through the winding of a magnet 228, the lower right-hand contact of sequence switch spring 210, and thence to the plus pole of battery at the right-hand armature of relay 117. Magnet 228 by attracting its armature presses the brush rod 212 against a low speed roller 229 rotating in the direction of the arrow, whereby the connector is moved in an upward direction but at a lower rate of speed than under the control of roller 211.

Upon the energization of relay 332 a circuit is closed from the plus pole of battery, through the front contact and armature of this relay, the left-hand contacts of sequence switch spring 339, conductor 427, the left hand armature and front contact of relay 413, conductor 615, the" armature and back contact of counting relay 1., and the winding of counting relay 1 to the minus pole of battery. Counting relay 1 becomes energized and closes a locking circuit for itself, including the winding of counting relay 1.

As above stated, as long as relay 332 is energized, counting relay 1 cannot become energized.

During the further upward travel of the connector 213, the commutator brush 21?) connects again plus battery, through the conducting plate 210, conductor 217, and the upper left-hand contact of sequence switch spring218, to the winding of relay 117, causing thus the deenergization of relay 332, whereupon counting relay 1 hecomes energized and shifts conductor 615 to the winding of counting relay 0, when upon this counting relay becomes energized and prepares the energizing circuit of the counting relay 0. In View of the fact, however, that in the meantime the al'iove-traced shunt path is open by virtue of the engagement of one of the insulated segments 230 by brush 215, the relay again pulls up its armature, preventing thus the energization of counting relay 0. As soon as the brush 215 again engages the conducting plate 216, the relay 332 becomes denergized and permits the energization of the counting relay 0. The fundamental circuit is then opened and relays 332 and 117 become deenergized. Upon the de'elnergization of relay 117 relay 202 and magnet 228 become dei nergized. The relay 202 closes a circuit through its left-hand back contact for driving the sequence switch 208 out of position 6 and into position 7 The deenergization of relay 117 results in the closure of the circuit through the right-hand back contact of this relay and the lower left-hand contact of sequence switch spring 118, whereby the sequence switch 106 is driven out of position 12 and into position 13. As soon as the sequence switch 106 reaches position 13, a circuit is closed from the plus pole of battery, through the left-hand contacts of sequence switch spring 113, the armature and front contact of relay 103, the lower left-h and contact of sequence switch spring 105, and the power magnet of sequence switch 106 to the minus pole of battery for driving this sequence switch out of position 13 and into position 14. In position 13 of sequence switch 106 and until the sequence switch is moved out of this position under the control of relay 103, a circuit is closed from ground, through the lower left-hand and upper right-hand contacts of sequence switch spring 183, lamp 184*, and the lower contact of sequence switch spring 199 to grounded battery. The steady lighting of lamp 184 indicates to the B operator that the A operator has not extended her cord circuit to the assigned trunk. In position 13 of sequence switch 106 the lamp 184 is included in a circuit traceable through the lower contacts of sequence switch spring 183. The lighting of this lamp indicates the completion of the setting of selector 122 and connector 213. In positions 15 to 18 of the sequence switch this lamp is again lighted, indicating to the operator that the subscribers are conversing.

In positions 13 to 15 of the sequence switch 106 a circuit is closed from the plus pole of battery, through the lower left-hand eon tact of sequence switch spring 120, and the right-hand winding of a relay 173 to ground. This relay does not respond to current flowing through this circuit, but is prepared for operation,-when its left-hand winding is included in a circuit from ground to the minus pole of battery. It the left-hand winding of relay 173 is included in a circuit to the plus pole of battery, this relay remains deenergized.

'hen the sequence switch 100 reaches position 14 and the sequence switch 208 position 7, a circuit is closed from the minus pole of battery through the winding of relay 202, the left-hand contact of sequence switch spring 201, conductor 200, terminal 149, wiper 148, the lower contact 01 sequence switch spring 147, the left-hand back contact and armature of a relay 157, the back contact and armature of relay 173, the left-hand back contact of a relay 152, the left-hand back contact and armature of relay 137, and the right-hand back contact and armature of relay 111 to the plus pole of battery. The relay 202 becomes energized and closes a circuit from the plus pole of battery, through its left-hand armature and front contact, a sequence switch contact 241, and the winding of a relay 231 to the minus pole of battery. The relay 231 becomes energized and closes a circuit from the plus pole of battery, through its left-hand armature and front contact, the lower contact of sequence switch spring 207, and the power magnet of sequence switch 208 to the minus pole of battery, for moving the sequence switch 208 out of position 7 and into position 10. As soon as the sequence switch 208 leaves position 7 and opens the left-hand contact of spring 201, the relay 202 is maintained energized by a circuit traceable from the-minus pole of battery, though its winding, the upper contact of sequence switch spring 210, the right-hand front contact and armature of relay 202, the lower right-hand contact of sequence switch spring 201, conductor 200, and through the selector 122 to the plus pole of battery at the right-hand armature of relay 111.

Let us suppose that the called line is idle, which fact is indicated by a full battery potential upon test terminal 233. Upon the setting of connector 213, a circuit is closed from the minus pole of battery, through the cut-01f relay individual to the called line, terminal 233, connector wiper 232, the righthand back contact and armature of relay 231, thelower left-hand contact of sequence right-hand back contact of relay 152 to,

ground. Relays 152 and173 become energized and the former closes a locking circuit for itself from ground through its righthand front contact and armature, low resistance 1efthand winding and thence through conductor 153 to the minus pole of battery at the cut-off relay of the called line. Due to the closure of this circuit, the potential on the test terminal 233 and multiples thereof is reduced so as to prevent the seizure of this line by another selector switch 122 and connector switch 213.

Upon the opening of the left hand back contact of relay 152, the locking circuit of relay 202 is opened and this relay, by releasing itsarmatures, closes a circuit from the plus pole of battery through its lefthand armature and back contact, the upper left-hand and lower right-hand contacts of sequence switch spring 203, and the power magnet of sequence switch 208 to the minus pole of battery, for moving this sequence switch out of position 10 and into position 12. A further result of the energization of relay 152 is the closure of a circuit from ground through the right-hand armature, front contact and the high resistance righthand winding of this relay, the left-hand winding of relay 157, the left-hand ar'mature and front contact of relay 152, the lefthand back contact and armature of rela 137, and the right-hand armature and bac I contact of relay 111, to the plus pole of battery. Relay 157 becomes energized.

In response to the energization of relay 157, a circuit is closed from the plus pole of battery through the lower right-hand contact of sequence switch spring 126, the right-hand frontcontact and armature of relay 157, and the right-hand winding of relay 137, to the minus pole of battery. The relay 137 becomes energized and opens the abpve traced circuitsof relays 152, 17 3 and 1.5

When the sequence switch 208 moves out the multiples of terminal 233' is reduced for preventing the seizure of this line by another selector switch.

Upon the energization of relay 137 a circuit is'closed from the minus pole of battery through the. power magnet of sequence switch 106, the upper contacts of sequence switch spring 138, the left-hand front contact and armature of'relay 137 and the righthand back contact and armature of relay 111, to the plus pole of battery. Due to the closure of this circuit the sequence switch 106 is moved out of position 14 and through position 15 into position 16. Although the relay 152 becomes deener ized the relay 157 remains locked up until t e sequence switch 106 moves out of position 15%. The locking circuit of this relay may be traced from the plus pole of battery, through the right hand armature and bacr contact of relay 111, a sequence switch contact 157, the left-hand armature, front contact and winding of relay 157, and the right-hand back contact of relay 152 to ground. Upon the deenergization of relay 157, the relay 137 becomes deenergized.

A circuit is now closed from ground, through the front contact and armature of relay 102, the upper contacts of a sequence switch spring 159, the winding of a ringing relay 160, the armature and back contact of a relay 161, the armature and back contact of a relay 162, the left-hand back contact and armature of relay 137 and the right-hand back contact and armature of relay 111 to grounded battery. Relay 160 becomes energized, relay 161 being prevented from becoming energized in series with relay 160 by virtue of a shunt placed around its winding, through its back contact and the back contact of relay 162. Upon energization, relay 160 closes the ringing circuit, which extends from a grounded ringing current source 163 through the right-hand winding of relay 162, the right-hand contact of sequence switch spring 16 1, the lower front contact and armature of relay 160, the lower contacts of sequence switch spring 156, wiper 151, terminal 150, conductor 219, the lower right-hand contact of sequence switch spring 218, wiper 234, the bell at the called subscribers station, connector wiper 235, the upper contact of sequence switch spring 201, conductor 200, terminal 149, wiper 148, the upper-right-hand contact of sequence switch spring 147, and the upper armature and front contact of relay 160 to ground. As soon as the called subscriber removes his receiver from the switchhook, the marginal relay 162 becomes energized and opens the shunt around the winding of relay 161, whereupon this relay becomes energized and shunts out relay 160. A

supervisory relay 165 is thereu on enerand closes a circuit'from grounded battery,

marked in heavy lines in Figs. land 2 ofv the drawings.

' As soon as the sequence switch 106 moves out of position 12 and opens the right-hand contacts of sequence switchspring 112, the relays .316 and 307' become denergized. The relay 307 closes a circuit from the plus pole .of battery, through its left-hand armature and back contact, the upper contact of sequence switch spring 304 and the power magnet of sequence switch 305 to the minus.

pole of battery, for driving this sequence switch out of position 16 and into position 17.- A circuit is thereupon closed from the minus pole of battery, through the winding of a magnet 341, the right-hand contacts of sequence switch spring 302 and the back contact and armature of relay 307 to the plus pole of battery. Magnet 341 becomes energized, and by attracting its armature presses the brush rod 310 against a roller 342, constantly rotating in the direction indicated by the arrow. The cord finder is thus returned to normal, and as soon as the commutator brush 320 .connects plus battery through a normal conducting segment 345, the right-hand contact of sequence switch spring 344 and the power magnet of sequence switch 305 to minus battery, this sequence switch is moved out of position 17 and into position 18, whereupon the circuit of magnet 341 is opened. Assuming that at this time the allotter 345 is standing in position 18, a circuit is closed from the plus pole of battery, throu glh sequende switch contact 346, allotter contact 347, and the power magnet of allotter 345 to the minus pole of battery for moving this allotter into position 1. A circuit is thereupon closed from the plus pole of battery, through the lower left-hand contact of allotter spring 348, the .-lower right-hand contact of sequence switch spring 340 and the power magnet of sequence switch 341 to the minus pole of battery. The sequence switch is moved out-of position.18 into position 1 and the cord finder is now again selected for service.

When disconnection is desired and the called subscriber restores his receiver to the switchhook, the relay 165 becomes deenergized and opens the circuit of relay 166 This relay'restores the original energizing circuit of relay 102, whereupon a. well-known 102 becomes denergized. Relay 103 also be- I comes denergized and closes a circuit from the minus pole of battery, through the lefthand contacts of sequence switch spring 112, the Winding of relay 108, the lower righthand and uEper'IeitJiand contacts of sequence switc spring 113, the armature and back contact of relay 103 and an interrupter 158 to plus pole of batter When the interrupter 158 completes .t is circuit, relay 108 becomes energized and connects the interrupter 158 through its right-hand front contact and armature, the upper contacts of sequenceswitch spring 109 and the winding of relay 111 to grounded battery. The relay 111 becomes energized and closes a locking circuit for itself through its left-hand front contact and armature and the sequence switch contact 114. The relay 111 closes also a circuit from the plus pole of battery, through its right-hand armature and front contact, the lower right-hand contact of sequence switch spring 105 and the power magnet of sequence switch 106 to the minus pole of battery for moving the sequence switch outof position 16 and into position 18. A circuit is now closed from the minus pole of batter through the winding of a magnet 168, t e lower contact of sequence switch spring 160, the. left-hand front contact and armature of relay 111, and the sequence switch contact 114 to the plus pole .of battery. Magnet 168 resses the brush rod 121 against a roller 1 0, constantly rotating in the direction indicated by the arrow. The selector 122 is thus returned to normal. As soonns the selector reaches its normal position, a circuit is closed from the plus pole of battery, through the upper contact'of sequence switch spring 126, commutator brush 132, a normal conducting segment 171, conductor 172, the upper righthand contact of sequence switch spring 113, and the power magnet of sequence switch 106, to the minus pole of battery, for moving the sequence switch out of position 18 and into position 1. Magnet 168 becomes deenergized, and due to the release of the selector 122, relays 202 and 204 become deenergized. The relay 204 closes a circuit from the plus pole of battery, through its left-hand armature and backcontact, the upper left-hand contact of sequence switch spring 20 7 and the power magnet of sequence switch 208 to the minus pole of battery,.for driving this sequence switch out of position 12 and into position 18. A circuit is now closed from the plus pole of'battery, through lower contact of sequence switch spring 221, and the winding of a magnet 236 to the minus pole of the roller 237 the connector is restored to,

normal. When it reaches its normal position, a circuit is closed from the plus pole oi battery, through brush 224, a comucting segment 238, the right-hand Contact of se-' quence switch spring 239, and the power magnet of sequence swltch 208 to the minus pole of battery. Sequence switch 208 is' moved out of position 18 and into position 1. Magnet 236 becomes denergized. Upon the movement of sequence switch 106 out of position 17, followed by the restoration of selector 122, and until the sequence switch 208 is moved out of position 18, the trunk leading to the connector is guarded against seizure by plus battery connected through a sequence switch contact 250, the right-hand back contact and armature of relay 204, resistance 205 and conductor 206 to test terminal 143 and multiples thereof.

It the called subscriber prematurely restores his receiver to the switchhook, and the A operator desires to rering his station, she causes relay 102 to vibrate its armature by pulling out and reinserting plug 100. The relay 102 opens the locking circuit of relay 161, whereupon this relay permlts the energization of ringing relay 160 and thus the reestablishment of the above traced ringing circuit. In response to each deenergization of relay 102, the relay 103 becomes denergized. In order to prevent the severing of the connection when the reringing of a party is desired, the interrupter is so timed that even if the relay 108 receives an impulse upon the deenergiaation of relay 103, it will be again energized by the time the interrupter is in position to send an impulse through its right-hand front contact and armature.

Overflow segments 370, 190 and 260 are provided on the commutator plates of the cord finder, selector and connector switches,

respectively. When the respective-commutator brushes of these switches engage the overflow segment, the switch is restored to normal in a manner that will be obvious from an inspection of the drawings and a consideration of the above description. When the commutator brush 132 engages the overflow segment 190, a circi-iit is closed from the plus pole of battery, through the upper contact of sequence switch spring 126, brush-132, segment 190, conductor 198, the upper contact of a sequence switch spring 199, a lamp 184, the lower contacts of se quence switch spring 159, and interrupter 182' to ground. The lamp 184' is flashed for giving the B operator the overflow signal- In the above description it was assumed that the called partys bell is responsive to stations rovided with bells ofthis type may be seize by settin the selector 122 in a manner to cause a rush 191 to engage an insulated portion 192 of a conducting, plate 193. If, however, a party line station is de-- sired, the bell of which is responsive only to current generated at a source 195, the selector 122 is set so as to permit the brush 191 to engage the conducting plate 193. A circuit is then closed from the plus pole of battery, through the upper contact of sequence swltch spring 126, brush 191, conducting plate 193, a conductor 194, the upper righthand contact of sequence switch s ring 136, and the right-hand winding of re ay 137 to the minus pole of battery. Due to the do sure of this circuit the relay 137 is maintained energized until the sequence switch is moved out of position 169; and irrespective of the condition of relay 157. The sequence switch is moved under the control of relay 137 into position 17, and the ringing circuit isthen established from the current source 195, through the left-hand contact of sequence switch spring 164.

If the B operator desires to hold the trunk shown in Fig. 1, she depresses a key 196, whereby the relay 103 is maintained energized irrespective of the condition of relay 102.

By depressing a key 197, the B operator may at .any time cause the energization of relay 111 while the sequence switch 106 is in positions 2 to 18. As above stated, the energization of relay 111 results'in the restoration of selector 122. 4

If the. called line is busy the poten ial on its test terminal 233 and multiples t ereof is reduced by virtue of a low resistance shunt path closed through a resistance like 242 or" the low resistance left-hand winding of a relay like 152. In this case upon the movement of the sequence switches 208 and 106 into positions 10 and 14 respectively, the marglnal relay 152 does not become energize but relay 173, which is not marginal, pulls up its armature. Due to the fact that relay 152 did not become energized the relay.

I current generated from source 163. Called back contact of relay 152, the left-hand back contact and armature of relay 137, and the ri ht-hand back contact and armature of re ay 111, to the plus pole of battery The sequence switch is moved out of position 14,

but, due to the fact that the lower left-hand contact of sequence switch spring 138 is opened as soon as the sequence switch leaves position 14, this sequence switch will stop in position 15. A circuit is now closed from" contact of relay 160, winding of relay 165,

the secondary winding of a repeating coil 176, and a resistance 177, to grounded battery. The relay 165 is intermittently eners gized and deenergized under'the control of the interrupter 175 and causes the vibration of the armatures of relay 166. The vibrationof the armature of relay 166 results in the flashing of a signal at the A operators position, whereupon this operator causes the release of the selector and connector switches in the same manner as above described.

Let us suppose that the called line is one of a plurality of lines leading to a private branch exchange. The test terminals of private exchange lines are differentiated from the test terminals of. direct lines by the connection of the plus instead of the minus pole of grounded battery through the cutoff relay of a private branch exchange line to the test terminals in the bank of the connegzor switch. The last private branch exchange line in a group is connected in the 1 same manner as a direct line, the minus pole of battery being connected to its test terminal. Upon the setting of the connector the marginal relay 152 becomes energized or remains deenergized, depending on the potential existing on the test terminal of called lines irrespective of the polarity of the battery connected to the test terminal. The relay 173, however, does not become energized when its left-hand winding is connected from ground to the minus pole of battery. For this reason, if the first private branch exchange line is busy, neither the relay 152 nor the relay 173 does pull up. Due to the fact that the relay 152 did not cause the en ergization of relay 157 relay 137 also remains deenergized. The relay 202 being maintained energized through the back contacts of the relays173, 152 and 157 in position 10 of sequence switch 208, the magnet 228 becomes again energized by current flowing through a circuit extending from the minus pole of battery through its winding, the lower right-hand contact of sequence switch spring 210, the right-hand front contact and armature of relay 202, the lower right-hand contact of sequence switch spring 201, conductor 200, terminal 149, wiper 148, the lower contact of sequence switch spring 147, lefthand back contact and armature of relay 157, left-hand back contact and armature of relay 173, left-hand back contact of relay 152, left-hand back contact and armature of relay 137, and the right-hand contact and armature of relay 111, to the plus pole of battery. Under the control of this magnet the connector is caused to further travel in an upward direction. As soon as the test wiper 232 encounters the test terminal of an idle PBX line, the relay 152 becomes energized,

opens the circuit of magnet 228, and causes the operation of sequence switch 106 in the same manner as above described in case of the seizure of an idle direct line. If, however, all the PBX lines are busy, then, as soon as the test terminal of the last PBX line is engaged by the test wiper of the connector, the relay 173 becomes ener ized due to the fact that the minus pole of Eattery is connected to such test terminal. The relay 152 being deenergized, the relay 173 controls the release of the switches in the same manner as above described in the case of a busy direct line.

If it is desired to seize the called line without regard to its busy or idle condition then, in addition to'the keys designating the digits of the called number, the B operator depresses also a key 530. A circuit is then closed from the minus pole of battery, through the lower right-hand contact of sequence switch spring 328, conductor 531, key 530, conductor 421, the left-hand winding of a relay 350, conductor 351, the upper contacts of sequence switch spring 402, the lefthand winding ofrelay 401, conductor 501, and the contact 500 of the thousands key No. 9, to the plus pole of battery. The relay 350 becomes ener ized and closes a locking circuit for itself rom the plus pole of battery, through sequence switch contact 352, its right-hand armature, front contact and right-hand winding to the minus pole of battery.

When the sequence switch 305 reaches position 16, a circuit is closed from ground through the left-hand armature and front contact of relay 350, the right-hand contact of sequence switch spring 335, the front 'conterminal 337, conductor 338, the winding of relay 154, sequence switch contact 17 8, and the right-hand back contact and armature of relay 117 to the plus pole of battery. The relay 154 becomes energized and locks up through its left-hand front contact and armature. The above traced circuit for relay 154 has a parallel path leading from sequence switch contact 178 through the lower left-hand contact of sequence switch spring 118 and the power magnet of sequence switch 106, to grounded battery. The sequence switch is moved out of position 12 and into position 13, through which position it is moved into position 14 in the same manner as above described. Relay 154 being energized, the relay 152 cannot become energized in response to the testing of the called line. The rela 154, however, closes a circuit from ground through the right-hand winding of relay 157," the right-hand front contact and armature of relay 154, the lower contact of sequence switch spring l40,'the right-hand armature and back contact of relay 137, conductor 155, and thence through the above traced circuit to grounded battery into position 16, whereupon the called line is' signaled and the connection is completed. I

What is claimed is: I

1. In a telephone exchange system, two lines,'means for rendering said lines busy, means including two selectively operable switching devices for preparing a connection between said lines, testing means for one of said devices associated with the other device, means dependent upon the busy or idle condition of one of said lines for actuating said testing means, and means operable in response to the actuating-of-said testing means for completing the connection at said one of said devices.

2. In a telephone exchange system, a-calling and a called line, means for rendering said called line busy, means including a sele'lor and a connector switch for preparing a connection between said lines, testing means for said connector switch associated with said selector switch and operable in accordance with the busy or idle condition of said called line, and means operable in response to the actuation of said testing means for completing the connection at said connector.

3. In a telephone exchange system, a line, another line and a third line, a selectively operable switching device for connecting said line to said other line, a second selectively operable switching device for preparing a connection between said other line and the third line, means for renderin said third line busy, a testing means for said second selectively operable switching device associated with said first mentioned selectively operable switching device and operable in accordance with the busy or idle condition of said third line, and means responsive to the actuation of said testing means for completing the connection between said, other line and the third line.

4. In a telephone exchange s stem, a callin and a called line, means or rendering said lines busy, a trunk line, a selector switch for extending the calling line to said trunk line, a connector switch for preparing a connection between said trunk line and called l1ne,test1ng means for said connector switch associated with said selector switch and operable in accordance with the busy or idle.

condition of said called line, and means responsive to the actuation of said testing means for completing a connection between said trunk line and called line.

l 5. In a telephone exchange system, two lines, means for rendering one of said lines busy, test terminals for said lines, means including a selectively operable switching device for extending. the other line toward said one of said lines, another selectively operof the condition of said one of said lines, and

a key for rendering inoperative said first test circuit and for rendering operative said sec- 0nd test circuit when said one of said lines is tested.

6. In a telephone exchange system, a calling and a called line, a trunk line, a switch for connecting the calling line to one end of said trunk line, another switch for connecting the called line to the other end of said trunk line, a test relay associated with the first-mentioned switch, a circuit for said test relay extending through both said switches, and means for operating said switches under the control of said test relay.

7. In a telephone exchange system, a calling and a called line, a trunk line, a switch for extending the calling line to one end of said trunk line, another switch for extending the called line to the other end of said trunk line, means for varying the electrical conditi-on of said called line, testing means associated with the first-mentioned of said switches, means for operating the same under a certain electrical condition of said called line, and separate means for operating said testing means.

8. In a telephone exchange system, two lines, a trunk line, a selectively operable switching device for connecting one of said lines to one end of said trunk line, another selectively operable switching device for connecting the other end of said trunk line to the other line, means for varying the elec- Y trical condition of said trunk line, means for varying the electrical condition of said other line, two test relays associated with the first-mentioned of said switching devices,'means for actuating one of said test relays depending on the electrical condition of said trunk line, means for actuating the other test relay depending on the electrical condition of said other line, an operating means for the first-mentioned switching device controlled by said one of said test relays, and an operating means for the secondmentioned switching device jointly controlled bysaid two test relays.

9: In a telephone exchange system, a calling line, a plurality of called lines, means for rendering said called lines busy, a selectively operable switching device for connecting said calling line to one end of said trunk line, another selectively operable switching device for connecting the other end of said trunk line to an idle one of said called lines, a test relay associated with the first one of said selectively operable switching devices for controlling the operation of said other switching device, and means depending on the busy or idle condition of the called lines for operating said test relay.

10. In a telephone exchange system, a calling line, a plurality of called lines, means for rendering said called lines busy, a selectively operable switching device for connecting said calling line to one end of said trunk line, means for rendering said trunk line busy, another selectively operable switching device for connecting the other end of said trunk line to an idle one of said called lines, a test relay associated with the first one of said selectively operable switching devices for controlling its operation, another test relay associated with said lastmentioned device for controlling jointly with said first-mentioned relay the operation of the other device, and means depending on the busy or idle condition of the called lines for operating said test relays.

11. In a telephone exchange system, a calling line, a plurality of called lines,

, means for rendering said called lines busy,

a selectively operable switching device for connecting said calling line to one end of said trunk line, another selectively operable switching device for connecting the other end of said trunk line to an idle one of said called lines, testing means associated with the first one of said selectively operable switching devices for controlling the operation of said other switching device, means depending on the busy or idle condition of the called lines for operating said testing means, and means for operating said testing means irrespective of the busy or idle condition of said called lines.

12. In a telephone exchange system, a plurality of calling lines, a selector switch having sets of movable and stationary contacts, means for extending a calling line to a set of movable contacts, groups of trunk lines terminating at one of their ends in said stationary contacts, 'means for electrically indicating the busy condition of a trunk at the set of contacts in which it terminates, means for operating said set of movable contacts to select a set of stationary contacts, a test relay associated with said selector switch, means operative in response to the idle condition of the selected trunk for operating said relay to arrest said movable contacts, a plurality of connector switches, movable contacts for said connector switches serving as terminals for the other ends of said trunk lines, a group of private branch exchange lines, a group of direct lines, party lines, sets of stationary contacts for said connector switches serving as terminals for said private branch exchange, direct and party lines, means for operating the movable contacts of said connector switches to select a set of said lastmentioned stationary contacts, another test relay at said selector switch, means under the joint control of said two test relays for controlling the seizure of a line selected by the movable contacts of any one of said connector switches, means including the other test relay associated with said selector switches and means associated with the said connector switches for holding the seized line, means for preventing the operation of said test relays upon the engagement by the connector of a line that is held, means operative upon the engagement of a seized private branch exchange line for causing the movable contacts of said connector to successively engage the stationary contacts of other private branch exchange lines until the last private branch exchange line is reached, a relay associated with said selector switch for controlling said last-mentioned means, two sources of ringing current of various frequencies at said selector switches, variably operable means at said selector switches for applying ringing cur-- rent of a certain frequency to a seized line, another relay associated with said selector, and means for operating said last-mentioned relay to control the seizure and holding of an already seized and held line.

In witness whereof I hereunto subscribe iliy zname this 27th day of January, A. I).

ALFRED H. DYSON. 

